During the recorded history of man, nitrogenous natural materials have been used as plant foods and animal feeds. The nitrogen in natural materials is usually present as one or more of a wide variety of proteins. These proteinaceous materials, when used as plant foods or animal feeds, decompose slowly into mineral nitrogen compounds which can be readily utilized by growing plants without damage to the environment in which they are used. They can also be effectively digested and utilized by animals consuming them.
As world population density has increased several important changes have occurred in the availability and use of the proteinaceous materials. Virgin nitrogenous natural materials are now usually too valuable for use as plant foods or animal feed supplements. Huge amounts of natural by-products and natural wastes are produced after the primary, and perhaps secondary, usages of the nitrogenous natural materials and present a large disposal problem. Most of this natural material is available in dilute, low bulk density, amorphous, mixed forms and are generally commercially unusable in agriculture. Some of these natural materials commonly available in excess are by-products and wastes from processing grains such as soybeans; and by-products from processing animals such as poultry, cattle, and swine. Other widely available nitrogenous natural materials are wastes from animals, and recovered sludges from sewage treatment plants.
In U.S. Pat. No. 3,655,395 John Karnemaat disclosed a process for treating industrial and municipal wastes suspended or dissolved in water by stepwise treatment with concentrated formaldehyde, nitric acid, and urea to form urea-formaldehyde condensation products which were then dried. Industrial and municipal wastes generally contain sufficient heavy metals to be unacceptable for many agricultural and environmental uses, and must be disposed of in special ways. Karnemaat extended his technology in U.S. Pat. No. 3,939,280 which teaches converting poultry manure to animal feeds by treatment with a catalytic amount of a non-toxic acid, such as sulfuric, phosphoric, citric, propionic and acetic, and with a formaldehyde supplying substance and urea. Although Karnemaat provided a step forward in the art of waste disposal, he did not recognize that natural nitrogenous materials could be caused to develop adhesive properties by heating under alkaline conditions, and that the natural materials could be formed into high integrity granules by mechanical means without polymerized urea-formaldehyde. Further, by adding substantial amounts of extraneous materials Karnemaat converted the initial natural organic material to a urea formaldehyde condensation product.
In U.S. Pat. No. 3,942,970 O'Donnell discloses a system for producing a granular, high nitrogen, odorless fertilizer from sewage filter sludge, which required addition of acid to bring the pH of the sludge to between 3 and 5, and then reacting it with methylolurea at pH 3-5, at 30.degree. to 80.degree. C. with vigorous agitation at temperatures of 30.degree. to 80.degree. C. to provide a granular reaction product of condensed urea formaldehyde polymer combined with the dried sludge. In U.S. Pat. No. 4,081,366 O'Donnell dewatered the urea formaldehyde-sludge mixture by means of vacuum filtration. The acid catalyzed reaction of O'Donnell denatures the natural proteins present in the sludge, thereby significantly reducing their effectiveness as animal feeds or fertilizers. No mechanical means was provided to produce high integrity granules from the natural materials. O'Donnell did not recognize that heating natural nitrogenous materials under alkaline conditions could provide the adhesive properties required to produce high integrity natural granules.
In U.S. Pat. No. 2,977,214, J. H. McLellan was able to produce granules of natural nitrogenous sewage sludge by compacting between high pressure rolls, breaking the compacted sludge and screening it. Unfortunately the particles referred to as granules were not dense, having a bulk density of only 35 pounds per cubic foot indicating a low degree of integrity.
The art has recently taken strong interest in the use of natural nitrogenous materials as plant food and animal feed supplements with a plethora of publications demonstrating their utility in agriculture. The products disclosed have largely been the result of composting, extrusion, compacting, pelletizing, or inclusion in resinous agglomerates. No teachings or suggestions have provided a method of forming these natural materials, wastes, and by-products into high integrity granules by heating under alkaline conditions until they develop adhesive properties.
Terms used herein are defined in the following list:
1. Natural nitrogenous materials--any substance occurring in nature formed by living organisms and containing nitrogen, including processing by-products and wastes, usually in the form of protein or complex organic nitrogen compounds such as uric acid.
2. High integrity--high degree of soundness, strength, and resistance to attrition.
3. Adhesive property--the capability of bonding surfaces together by surface attachment.
4. Water soluble nitrogen--soluble in water as defined by the Association of American Plant Food Control Officials (AAPFCO).
5. Harden--to make not soft but solid and firm to touch.
6. Liquid phase--the liquid portion of a mixture containing liquid and solid under process conditions.
7. Chopper--device for cutting into small pieces by hitting with sharp knives or bars.
8. Substantial--large enough to affect physical properties.
9. Percent--weight percent.
10. Agriculture--the industry of producing crops and animals employing plant foods and animal feed supplements.
11. Basic Conditions--where pH is between 7 and 14.
12. Base--class of compounds producing pH's between 7 and 14 and having the ability to neutralize acids.
13. Agricultural Nutrient Substances--synthetic or natural materials normally used in the field of agriculture as plant nutrients or animal feed supplements.